The present invention relates to devices and methods for measuring moisture in hay and similar crops and, in particular, the present invention relates to devices and methods for measuring moisture in hay during a baling process.
Hay, a major crop for feeding livestock, is commonly prepared by cutting alfalfa or grass stems near the ground, allowing the newly cut material to air dry on the ground for a period of time, and then subsequently harvested by a hay baler. One type of hay balers in common use functions to package hay into a compressed unit, often a rectangular package, by packing the crop into a chute, tying twine around the bale and then discharging the finished bale. Since hay will spoil in a bale with a moisture content above about 18 percent (weight per weight), knowing the moisture of the hay being baled is important. Moisture content of the hay, particularly while drying on the ground prior to baling, is subject to rapid changes as wind and sun can quickly remove moisture from the crop or as rain or dew can quickly add moisture to the crop. One practical method of determining hay moisture would employ a test instrument that provides accurate and rapid readings in the field to help determine the suitability of the crop to be baled.
Electronic moisture testers are in common use in the production of hay to provide meaningful and quick references to the moisture of the hay. The common forms of electronic testers include hand held instruments with a probe to insert into the hay baler, a portable canister unit to fill with the hay to be sampled, or a two point sensor mounted on the baler with the sensors connected to a readout module. Typically, a readout module is located in the cab of the tractor pulling the baler. All electronic testing units in common use currently employ direct current power at a low level, usually around five volts, to send a signal out through one electrode in contact with the hay bale being measured. The most common type of tester then reads the amount of voltage reaching a second electrode in contact with the bale. This reading is directly related to moisture content of the hay and is scaled in a readout to indicate the moisture content of the crop. A variation on this method is to read the impedance of voltage sent through one electrode. Such impedance is also related to the moisture content of the crop and may therefore be scaled and read as a moisture number by an instrument connected to the electrode.
Recently, the most popular method of reading electronic moisture has been to employ a sensor using the two electrode points sensors mounted on the interior pathway of a hay baler. This type of sensor uses one point as the voltage source electrode and the other point as the voltage receiving electrode. Normally, both electrodes are mounted along the pathway of the baler using a single non-conductive pad that isolates each bolt from the other and from other conductive materials in the baler. As hay passes by the non-conductive pad with two electrodes, voltage is conducted from one electrode to the other electrode. As the moisture increases in the hay, conductivity increases giving a signal which can then be scaled and read in the cab of the tractor as the baler is operated.
A sensor arrangement with a single non-conductive pad and two electrodes might be expected to provide a satisfactory method of sensing hay moisture. Investigative field tests were carried out to assess performance of such prior art sensors. Specifically, a variety of hay bales with different moisture content were tested using less convenient, but more dependable and accepted analytical moisture determination methods and comparing such analytical moisture tests to the readings generated by a conventional prior art sensor with two electrode mounted upon a single pad with the following surprising results:
Clearly, the results show that the tested prior art sensor was unacceptable.
The observed short-comings of a sensor with a single non-conductive pad bearing two electrode were considered and attributed by the present inventor to four different effects which are detrimental to reliable hay moisture measurement. First, the observed conductivity measurement from the pad with two electrodes arrangement is effected by the amount of pressure of the hay against the non-conductive pad and its electrodes. Specifically, in practice, the single non-conductive pad with two electrodes generates higher conductivity readings at higher hay pressures. The higher conductivity readings can be misinterpreted as higher moisture content percentages. Accuracy of the moisture reading is therefore significantly effected and compromised by changes in bale compression pressure. Second, accuracy is also adversely effected by static electricity build up caused by hay rubbing against the two electrodes and the associated non-conductive pad. Third, accuracy is also effected by any organic residue left on the electrodes from the hay going past the non-conductive pad and two electrodes. Fourth, accuracy is also subject to be adversely effected by the location of the pad relative to the passing bale when the single surface region of contacting the electrodes is not representative of an entire bale""s hay content.
The prior art sensor system, employing a non-conductive pad and two electrodes is undependable for hay moisture measurement. A better moisture measurement device and method which addresses the deficiencies of sensors with a single non-conductive pad and two electrodes has now been invented.